The proposed research seeks to determine what conditions govern the strength of the aggressive reactions resulting from an aversive occurrence. It is generally assumed that unpleasant happenings produce a readiness for aggression, whether the events are frustrations (barriers to the attainment of anticipated goals) or painful stimuli. However, the readiness need not lead to an open attack upon some potential target. Aggression is most likely to appear under some circumstances. In looking into the consequences of frustrations, we will inquire into the effects of such factors as what response the thwarted person is set to perform immediately after the frustration occurs, the extent to which he had previously acquired an attitude of learned helplessness so that he does not believe himself capable of reaching his goals, and what thoughts he has about his tormentor following the frustration. In the research on the aftereffects of physical pain we will attempt to determine whether conditions governing aggressive reactions to thwartings also influence aggressive reactions to pain. We will investigate the consequences of such things as the degree to which the available target is associated with other unpleasant events, the extent to which the pained individual believes he can successfully terminate the noxious event, and the direction of this person's attention after he is exposed to the noxious stimulus. In all of these studies it is generally assumed that the above-specified factors heighten the chances that overt aggression will occur but are not necessary for aggression. If the subjects are sufficiently uninhibited at the time and if the measures are sufficiently sensitive, the results may show that many aversive events produce an inclination to aggression. Still other research will ask how the target's reactions after he is attacked affect the aggressor's subsequent behavior, and what conditions influence the persistence of the attacker's aggressive tendencies.